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Item Type: Tesi di dottorato
Resource language: English
Ferone, Mariateresamariateresa.ferone@unina.it
Date: 5 January 2018
Number of Pages: 129
Institution: Università degli Studi di Napoli Federico II
Department: dep19
Dottorato: phd012
Ciclo di dottorato: 30
Coordinatore del Corso di dottorato:
Sannia, Giovannisannia@unina.it
Marzocchella, AntonioUNSPECIFIED
Date: 5 January 2018
Number of Pages: 129
Keywords: biofilm, succinic acid, lignocellulose
Settori scientifico-disciplinari del MIUR: Area 03 - Scienze chimiche > CHIM/11 - Chimica e biotecnologia delle fermentazioni
Area 09 - Ingegneria industriale e dell'informazione > ING-IND/25 - Impianti chimici
Date Deposited: 16 Jan 2018 09:50
Last Modified: 14 Mar 2019 11:56
URI: http://www.fedoa.unina.it/id/eprint/12272

Collection description

The study carried out during the present Ph.D. program aimed at investigating succinic acid production by fermentation. The work was carried out at the Dipartimento di Ingegneria Chimica, dei Materiale e della Produzione Industriale of the Università degli Studi di Napoli ‘Federico II’. The commercial strain Actinobacillus succinogenes DSM 792 was selected for its ability to produce succinic acid at high concentration and yield from a broad variety of carbon source. The activities were articulated along the two paths described hereinafter. Characterization of the succinic acid fermentation process as regards the concentration and yields The study was aimed at the assessment of the fermentation performance - in terms of succinic acid concentration and yield – with reference to two classes of feedstocks: 1) sugars typically present in lignocellulosic hydrolysates (glucose, mannose, arabinose and xylose); 2) high sugar content beverages (HSCBs). The investigations were carried out with batch fermentation of free A. succinogenes cells at different sugar concentration. The conversion process was characterized in terms of metabolite production (succinic acid, formic acid and acetic acid), sugar conversion, pH and cell concentration. The study included tests with single sugar and sugar mixtures (synthetic and commercial): i) glucose, mannose, arabinose and xylose (GMAX) to mime the composition of a lignocellulosic hydrolysate; ii) sucrose, glucose and fructose (SGF), the sugars typically present in leftover beverages. All the investigated sugars were converted in succinic acid by A. succinogenes. Tests with mixtures pointed out that the fermentation took advantage of the co-presence of different sugars with respect to the tests carried out with single sugars. The synergy effect of the sugars led to an increase in final succinic acid concentration and SA selectivity. Development of a continuous process for the succinic acid production Continuous fermentation tests carried out in a CSTR were aimed to the systematic characterization of the kinetics of cell growth and succinic acid production. The continuous fermentation were carried out by feeding the CSTR with a glucose bearing medium at a wide interval of dilution rate. The kinetics of A. succinogenes growth on glucose was investigated by assessing the effects of glucose and acids - succinic, acetic, and formic - on cell growth. The experimental results were successfully correlated by a multiple product-inhibited interacted growth model. Experimental results pointed out the individual inhibitory effect of the acids on A. succinogenes growth. Under the investigated operating conditions, results pointed out that: no substrate inhibition was observed; acetic acid did not inhibit the cell growth and the succinic acid production. The activity aimed at the intensive succinic acid production regarded the design, set-up, operation and optimisation of a packed bed biofilm reactor (PBBR). The effects of the operating conditions - dilution rate (D) and medium compositions (glucose, GX, xylose, GAX) - on the PBBR performances were investigated. Succinic acid concentration, productivity and sugar(s) conversion generally decreased with D. A maximum succinic acid productivity of 35.0 g/L*h was achieved at a D= 1.9 h-1. The effect of HMF and furfural, the main inhibitors found in lignocellulosic hydrolysate, on succinic acid production was also investigated. HMF resulted to have a higher inhibition effect on succinic acid production compared to furfural.


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